The pharmacopeial evolution of intralipid injectable emulsion in plastic containers: From a coarse to a fine dispersion

On December 1, 2007, the United States Pharmacopeia (USP) adopted Chapter 〈729〉 entitled Globule Size Distribution in Lipid Injectable Emulsions that contains two globule sizing methods and criteria to measure the mean droplet diameter (MDD) and the large-diameter tail of the globule size distribution to meet pharmacopeial specifications. The first of these measures, as the intensity-weighted MDD expressed in nanometers, must be less than 500 nm. The second measure, as the volume-weighted percentage of fat greater than 5 μm or PFAT5, must be less than 0.05%. These limits were first suggested in 2001 based on an analysis of 16 lipid injectable emulsions available worldwide. In 2004, the packaging of the innovator lipid emulsion product Intralipid™ was changed from conventional glass bottles to plastic containers in the U.S. A subsequent analysis of the emulsion in its new container showed it to be more coarse than its previous glass counterpart and now failed the PFAT5 limit. In 2007, it was announced that Intralipid™ in plastic containers was reformulated to meet the pharmacopeial limits. To track the time course of its transition from a coarse to a fine dispersion, 31 lots of Intralipid with expiration dates spanning five years were investigated.